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11 INSTRUCTIONS AND FUNCTIONS
Processing Code 33
11 - 420
Reading the ON/OFF status of the CS (CTR), DSR (DR), RS (RTS), DTR (ER)
and CD control signals
Control table format definition
Element position
Item
%(0)
Processing code
%(1)
CS (CTS) and DSR
(DR) control signals
%(2)
RS (RTS) and DTR
(ER) control signals
%(3)
CD control signal
• This processing code is used to read the ON/OFF status of the CS (CTR), DSR
(DR), RS (RTS), DTR (ER) and CD control signals of an open communication
channel.
• Specify 33 for the processing code.
• The CS (CTR) control signal cannot be read for the RS-232C interface
(CH1/CH2).
Because the DSR (DR), DTR (ER) and CD control signals are not included in
RS-422/485(CH3), they cannot be read for the interface.
• The ON/OFF status of each control signal is expressed in the following manner
using the higher and lower 8 bits:
(Ignore these bits.)
It is convenient to use the RDSET instruction to read the bits since only
the least significant bit of the lower and higher bytes in the array elements
is used for the ON/OFF status of each control signal.
Higher byte
%(1)
Can be read by the instruction
RDSET(8,
Description
Specify the processing code.
Read the status of the CS (CTS) and DSR (DR)
control signals into the lower and higher bytes,
respectively.
Read the status of the RS (RTS) and DTR (ER)
control signals into the lower and higher bytes,
respectively.
Read the status of the CD control signal into the
lower byte.
Status of
control signal
Lower byte
Can be read by the instruction
%(1)).
RDSET(0,
MELSEC-Q
1:ON
0:OFF
%(1)).
11 - 420
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